I don't think that's what you would want to do. Parquet will eventually compress large values, but not after making defensive copies and attempting to encode them. In the end, it will be a lot more overhead, plus the work to make it possible. I think you'd be much better of compressing before storing in Parquet if you expect good compression rates.
On Fri, Apr 5, 2019 at 11:29 AM Brian Bowman <brian.bow...@sas.com> wrote: > My hope is that these large ByteArray values will encode/compress to a > fraction of their original size. FWIW, cpp/src/parquet/ > column_writer.cc/.h has int64_t offset and length fields all over the > place. > > External file references to BLOBS is doable but not the elegant, > integrated solution I was hoping for. > > -Brian > > On Apr 5, 2019, at 1:53 PM, Ryan Blue <rb...@netflix.com> wrote: > > *EXTERNAL* > Looks like we will need a new encoding for this: > https://github.com/apache/parquet-format/blob/master/Encodings.md > > That doc specifies that the plain encoding uses a 4-byte length. That's > not going to be a quick fix. > > Now that I'm thinking about this a bit more, does it make sense to support > byte arrays that are more than 2GB? That's far larger than the size of a > row group, let alone a page. This would completely break memory management > in the JVM implementation. > > Can you solve this problem using a BLOB type that references an external > file with the gigantic values? Seems to me that values this large should go > in separate files, not in a Parquet file where it would destroy any benefit > from using the format. > > On Fri, Apr 5, 2019 at 10:43 AM Brian Bowman <brian.bow...@sas.com> wrote: > >> Hello Ryan, >> >> Looks like it's limited by both the Parquet implementation and the Thrift >> message methods. Am I missing anything? >> >> From cpp/src/parquet/types.h >> >> struct ByteArray { >> ByteArray() : len(0), ptr(NULLPTR) {} >> ByteArray(uint32_t len, const uint8_t* ptr) : len(len), ptr(ptr) {} >> uint32_t len; >> const uint8_t* ptr; >> }; >> >> From cpp/src/parquet/thrift.h >> >> inline void DeserializeThriftMsg(const uint8_t* buf, uint32_t* len, T* >> deserialized_msg) { >> inline int64_t SerializeThriftMsg(T* obj, uint32_t len, OutputStream* >> out) >> >> -Brian >> >> On 4/5/19, 1:32 PM, "Ryan Blue" <rb...@netflix.com.INVALID> wrote: >> >> EXTERNAL >> >> Hi Brian, >> >> This seems like something we should allow. What imposes the current >> limit? >> Is it in the thrift format, or just the implementations? >> >> On Fri, Apr 5, 2019 at 10:23 AM Brian Bowman <brian.bow...@sas.com> >> wrote: >> >> > All, >> > >> > SAS requires support for storing varying-length character and >> binary blobs >> > with a 2^64 max length in Parquet. Currently, the ByteArray len >> field is >> > a unint32_t. Looks this the will require incrementing the Parquet >> file >> > format version and changing ByteArray len to uint64_t. >> > >> > Have there been any requests for this or other Parquet developments >> that >> > require file format versioning changes? >> > >> > I realize this a non-trivial ask. Thanks for considering it. >> > >> > -Brian >> > >> >> >> -- >> Ryan Blue >> Software Engineer >> Netflix >> >> >> > > -- > Ryan Blue > Software Engineer > Netflix > > -- Ryan Blue Software Engineer Netflix
